1. Technical Field
The present invention relates to microwave-employing hyperthermia treatment devices and treatment systems.
2. Description of the Related Art
That a one-degree rise in human body temperature increases immunological competence by 30% is conventional knowledge, and a variety of thermotherapeutic techniques taking advantage of that fact are available. With microwave treatment devices, an extremely weak output is used for treating arthritis, chronic rheumatism, and similar diseases.
Achieving necrosis of cancerous tumors by putting the human body into hyperthermia of about 43° C. is also conventional knowledge. There are a variety of means by which the body can be put into hyperthermia, among which raising temperature by exposing the body to microwave energy is known.
A specific such example is in Japanese Unexamined Pat. App. Pub. No. S61-33668, in which an affected part of a patient's body is exposed to microwave energy at 2,450 MHz so as to continuously heat the affected part at about 43° C. for about an hour, and the process is repeated at regular intervals.
As an improvement in microwave hyperthermia techniques, Japanese Unexamined Pat. App. Pub. No. H05-23400 discloses an implementation comprising a first control means for controlling the number of microwave output pulses, and a second control means for controlling the output level.
This embodiment is configured such that microwave energy is output in synch with the power supply frequency, rendering the provision of a separate oscillator unnecessary. The number of pulses per second is changed by adjusting an output-adjusting dial. Accordingly, in the case of a 50 Hz commercial power supply, since the number of pulses output per second is 50, the per-second pulse count can be adjusted from 1 to 50 with the control dial.
As the dial is turned to make the adjusted output value greater, the number of microwave pulses output per second increases, along with which the wave height decreases. Conversely, as the dial is turned to make the adjusted output value smaller, the number of microwave pulses output per second decreases, along with which the wave height increases. Pat. App. Pub. No. H05-23400 states that accordingly, setting the output-adjusting dial to a low value enables a large dose of energy to be applied to biological tissue within a short period of time, whereby the biological tissue can be heated to deep-layer areas.
Further, the disclosed technique controls the microwave output energy with two control means so as to reduce the microwave output-power level along with an increase in the number of output pulses.
Meanwhile, Japanese Unexamined Pat. App. Pub. No. H08-206242 discloses technology for heating both deeper and surface areas by outputting microwave energy in intermittent pulses in alternation with a continuous pulse. This technology is embodied so as to output microwave energy in synch with the power supply frequency. Setting of the microwave output-power value per interval during which the microwave energy is output in intermittent pulses is done with pulsed-output count and power-level adjustments, and the setting per interval that the microwave energy is output in a continuous pulse is done with the power-level adjustment.
Therein, assuming that the ratio of the interval during which the microwave energy is output in intermittent pulses to the interval during which the microwave is output in a continuous pulse is 1:1 (=5 seconds:5 seconds), the disclosure teaches that in a 5-second period for the intermittent-pulse microwave output interval, five intermittent microwave pulses of 0.2 seconds pulse width are output with the power level being set to 500 watts, and in the ensuing 5-second period for the continuous-pulse microwave output interval, the power level is set to 100 watts.
In this conventional example, the output energy in the case of the intermittent pulses is 500 W×(0.2 s×5)=500 J, and the energy in the case of the continuous pulse is 100 W×5 s=500 J; thus the output energy of both the intermittent pulses and the continuous pulse is the same.
Since the output energy reaching an affected part is attenuated within a subject's body, with thus attenuated output energy levels, although it may be termed thermotherapy, the technology is unable to achieve necrosis of cancerous tumors.
In a still further example of hyperthermia treatment using microwave energy, Japanese Unexamined Pat. App. Pub. No. 2001-231870 discloses technology with a first oscillating means that outputs electromagnetic radiation at a first oscillation frequency, a second oscillating means that outputs electromagnetic radiation at a second oscillation frequency, and a mixing means that mixes and outputs simultaneously the electromagnetic radiation of the first and the second frequencies, wherein an affected area of a subject is exposed with the mixed-frequency electromagnetic radiation to heat the affected area.
In particular, high-frequency (2450 MHz) electromagnetic waves and low-frequency (915 MHz) electromagnetic waves differ in their tissue-depth attainment levels—that is, in their attenuation rates within tissue. Given that low-frequency electromagnetic radiation has a lower attenuation rate in tissue and can reach further than high-frequency electromagnetic radiation, electromagnetic waves at the two frequencies are mixed by the mixing means at a ratio of choice, and through an antenna section are irradiated onto the prostate area.
More specifically, with the technology disclosed in Pat. App. Pub. No. 2001-231870, the mixing ratio for the two frequencies of electromagnetic radiation is preset in accordance with the weight of the prostate. For example, if the prostate weighs less than 20 g, with 2450 MHz:915 MHz being a 9:1 ratio, and assuming a total output power of 50 W, then the proportions would be 45 W:5 W. Likewise, if the prostate weighs 40 to 50 g, with the ratio being 3:7 and assuming a the total output power of 50 W, the proportions would be 15 W:35 W.
Nevertheless, the conventional techniques discussed above each employ a single microwave treatment device and irradiate microwaves continuously for approximately one hour. Consequently, patients undergoing hyperthermia treatment must endure the high temperature for as long as an hour or so.